Battery condition indicators are used in lead/acid storage batteries of many types, including those installed in motor vehicles. Known battery condition indicators function as hydrometers detecting changes in the specific gravity indicative of the electric charge condition of the battery and provide a visual indication of the charge condition. Battery condition indicators also can detect changes in electrolyte level of the battery and provide a visual indication if the electrolyte level is below a predetermined minimum level. It is known to provide both charge condition detection and electrolyte level detection functions in the same battery condition indicator.
A known battery condition indicator is inserted in the cell of a battery and provides a head with a visual window for looking into the indicator. A cage or box is immersed in the fluid electrolyte, if the battery is adequately filled. One or more colored floatable indicator bodies are contained in a channel or channels in the cage and respond to different battery conditions to rise or fall in the channels. A light transmissive rod extends between the head of the indicator and the cage with the floatable bodies. A conical tip at the end of the light transmissive rod has a tip adjacent the channels in which the one or more floatable bodies move. The floatable bodies are of different colors to provide different visual queues when visible through the indicator. A battery condition indicator having one floatable body indicator can provide visual queues for a satisfactorily charged battery with satisfactory electrolyte level, a different visual queue for a satisfactory electrolyte level but a low battery charge and a third queue if the electrolyte level is low. By providing more floatable bodies responsive to different specific gravities, high and low fluid levels can be indicated as well as low, fair and satisfactory electric charge.
Battery condition indicators as described have worked well, but are not without disadvantages. Light transmissive rods used in the indicators have been straight, shaft-like bodies of molded plastic. Rods of small diameter provide a small visual queue of the condition of the battery. The small diameter visual queue can be difficult to perceive accurately, and requires users to understand a color code system of indicated conditions. Rod-shaped transmissive bodies can be damaged during handling, before installation in a battery. A small, hair-line crack that is undetected before installation can propagate over time, causing the indicator to fail in the battery. Injecting plastic into a rod-shaped form can be difficult. If the transmissive body is made of relatively greater diameter, the increased material across the diameter can be slow to cool, increasing cycle times for production. Injection site defects can lead to the problem of crack propagation described above. Straight cylindrical rods can be difficult to align properly in the receiving hole in a battery. Misalignment can result in inadequate sealing in the hole, potentially resulting in fluid loss.
What is needed in the art is a light transmissive body for battery condition indicators that is stronger than known bodies, provides a better visual queue for indicating the status of the battery and is less prone to failure after installation.